1. CISC AND RISC SYSTEM
Based on instruction set, we broadly classify Computer/microprocessor/microcontroller into CISC and RISC. CISC SYSTEM: COMPLEX INSTRUCTION SET COMPUTERS: Generally, there are a large number of instructions, each of which has a different permutation of the same operation(like data access, data transfer etc.) or are capable of multi-step operations or addressing modes within single instructions.
Permutation- fundamental change
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Micro 8051

2. Continues…
This gives the programmer flexibility in writing the program, But it occupies more memory.
There was a need to reduce the number of instruction per program.
This was achieved by having multiple operations within single instruction.
Multiple operations lead to many different kinds of instructions.
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Micro 8051

3. Continues…
Access to memory in turn makes the instruction length variable and fetch decode execute time unpredictable.
Making it more complex, thus hardware was made to understand the complexity of instruction set.(Complexity is in Micro program)
Intel 8051 is an example of CISC architecture.
Other examples are 8085,8086,MC 6800, Z-80
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Micro 8051

4. CHARACTERISTICS OF CISC SYSTEM:
Large number of instructions: around instructions.
A large number of addressing modes, variable length instruction formats
Execution time for an instruction may take several clock cycles so instruction timing is also different.
Efficient use of memory.
No or less pipelining.
Complexity is in Micro program.
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Micro 8051

5. RISC SYSTEM
In applications which require more of input , output related operations having few simple instructions that are of the same length allows memory access only with explicit load and store instructions.
Hence each instruction performs less work but instruction execution time among different instructions is consistent.
This would lead to instruction execution by hardware including multiple number of registers inside CPU.
The computer using such instructions is called Reduced Instruction Set Computer (RISC).
PIC microcontroller manufactured by Microchip Company is an example for RISC architecture.
Explicit- Stated Clearly or Precisely
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Micro 8051

6. CHARACTERISTICS OF RISC SYSTEM:
Relatively few instructions, instruction are fixed length.
Instructions are executed in small clock periods, hence they are faster than CISC.
Very few addressing modes.
Limited memory access made available to certain instruction.
Highly Pipelining.
21-Nov-18
Micro 8051

7. COMPARISON CISC RISC Complex instructions taking multiple cycles.
Simple instructions taking one cycle
Most of the instructions refer memory.
Very few instructions refer memory
Instructions are executed by micro program
Instructions are executed by hardware
No or Less Pipelined
Highly pipelined
Variable format instructions
Fixed format instructions
Single Register Set
Multiple Register Set
Examples 8085,8086, Pentium (Intel),M6800 (Motorola),Z-80 (Zilog),and microcontroller (8051 series intel)
PIC microcontroller from microchip, ARM, Power PC.
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Micro 8051

8. Difference between Harvard and Von- Neumann
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Micro -PIC

9. Von-Neumann/Princeton architecture
It uses a single memory space for both instructions and data. It is also called a stored-program computer.
It has limited data transfer rate.
This seriously limits the effectively processing speed when the CPU is required to perform minimal processing on large amount of data.
Most processor like 8085,8086,M6800, use this architecture

10. Harvard Architecture
Physical separate storage and signal pathways for instructions and data.
The CPU can both read an instruction and perform a data access at the same time.
A Harvard architecture computer can thus be faster for a given circuit complexity because instruction fetches and data access do not use a single memory.

11. Continues…
Harvard architecture are also frequently used in specialized DSPs,Commonly used in audio or video processing products.
Most general purpose small microcontrollers used in many electronics applications, such as PIC microcontrollers by MICROCHIP TECHNOLOGY,INC and AVR BY ATMEL CORP.
These processors are characterized by having small amount of program and data memory, and take the advantage of the HARVARD ARCHITECHTURE.

12. HARVARD ARCHITECTURE (PIC 16c6x/7x )
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Micro -PIC

13. COMPARISON B/W HARVARD AND VON-NEUMANN ARCHITECTURE
HARVARD ARCHITECTURE
VON-NEUMANN/PRINCETON ARCHITECTURE
This architecture consists of separate program and code memory.
It consists of common program and code memory.
Execution of instructions are faster, because fetching of code and data are separate.
Execution of instructions is relatively slow ,because not possible to fetch code and data simultaneously.
Execution of instruction takes less instruction (machine) cycle.
Execution of instruction takes more instruction (machine) cycle.
Use RISC processor
Use CISC processor
This is greater amount of parallelism
This is no need to have parallelism
Chip design is complex because of separate memory.
The largest advantages is that it simplifies the chip design because only one memory is accessed.
Eg: General microcontrollers (PIC), Special DSPs.
E.g. Motorola -68HC11 microcontroller,8085,8086, MC6800.

14. COMPUTER SOFTWARE
A set of sequential instructions is written to perform any task by a computer , it is called Computer program.
The different types of languages are developed, in order to communicate with computers is called Programming languages or computer languages.
Machine language
Assembly language
High level language

15. Types of programming languages
Machine language:
The computer can understand only machine language which uses 0s and 1s.
All instructions,memory,number,characters in strings of 0s and 1s.
Opcode: Tells which operations to be performed
Operand:Tells operation to be performed on which data.
OPCODE
OPERAND

16. Continues… Assembly language:
It uses symbolic instruction and executable machine codes.
Assembler: Assembly language instruction to machine language instruction.
General format:
[Label:] mnemonic [Operands] [; comment]
Eg: START:MOV A,B ; MOVE B TO A

17. Continues… High level language:
This language consists of set of instructions like words and symbol.
The specified rules are to be followed while writing programs.
INTERPRETERS OR COMPILERS: High level language to machine level language.